Add interface for [NotificationXmlContent]

Author: Sergio0694

Microsoft.Toolkit.Uwp.Notifications/Adaptive/Elements/Element_AdaptiveText.cs

@@ -7,7 +7,7 @@
 
 namespace Microsoft.Toolkit.Uwp.Notifications.Adaptive.Elements
 {
-    internal sealed class Element_AdaptiveText : IElement_TileBindingChild, IElement_AdaptiveSubgroupChild, IElement_ToastBindingChild, IHaveXmlName, IHaveXmlNamedProperties
+    internal sealed class Element_AdaptiveText : IElement_TileBindingChild, IElement_AdaptiveSubgroupChild, IElement_ToastBindingChild, IHaveXmlName, IHaveXmlNamedProperties, IHaveXmlText
     {
         internal const AdaptiveTextStyle DEFAULT_STYLE = AdaptiveTextStyle.Default;
         internal const AdaptiveTextAlign DEFAULT_ALIGN = AdaptiveTextAlign.Default;

…rialization/IHaveAdditionalProperties.cs …lization/IHaveXmlAdditionalProperties.csMicrosoft.Toolkit.Uwp.Notifications/Common/Serialization/IHaveAdditionalProperties.cs renamed to Microsoft.Toolkit.Uwp.Notifications/Common/Serialization/IHaveXmlAdditionalProperties.cs Microsoft.Toolkit.Uwp.Notifications/Common/Serialization/IHaveAdditionalProperties.cs renamed to Microsoft.Toolkit.Uwp.Notifications/Common/Serialization/IHaveXmlAdditionalProperties.cs

@@ -11,7 +11,7 @@ namespace Microsoft.Toolkit.Uwp.Notifications;
 /// <summary>
 /// An interface for a notification XML element with additional properties.
 /// </summary>
-internal interface IHaveAdditionalProperties
+internal interface IHaveXmlAdditionalProperties
 {
     /// <summary>
     /// Gets the mapping of additional properties.

Microsoft.Toolkit.Uwp.Notifications/Common/Serialization/IHaveXmlContent.cs

@@ -0,0 +1,16 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace Microsoft.Toolkit.Uwp.Notifications;
+
+/// <summary>
+/// An interface for a notification XML element with an explicit XML text content.
+/// </summary>
+internal interface IHaveXmlText
+{
+    /// <summary>
+    /// Gets the text content of the current element.
+    /// </summary>
+    string Text { get; }
+}

Microsoft.Toolkit.Uwp.Notifications/Common/XmlWriterHelper.cs

@@ -55,7 +55,7 @@ public static void Write(System.Xml.XmlWriter writer, object element)
                 // If it's a content attribute
                 else if (attributes.OfType<NotificationXmlContentAttribute>().Any())
                 {
-                    content = propertyValue;
+                    continue;
                 }
 
                 // Otherwise it's an element or collection of elements
@@ -68,7 +68,9 @@ public static void Write(System.Xml.XmlWriter writer, object element)
                 }
             }
 
-            foreach (var property in (element as IHaveAdditionalProperties)?.AdditionalProperties ?? Enumerable.Empty<KeyValuePair<string, string>>())
+            content = (element as IHaveXmlText)?.Text;
+
+            foreach (var property in (element as IHaveXmlAdditionalProperties)?.AdditionalProperties ?? Enumerable.Empty<KeyValuePair<string, string>>())
             {
                 writer.WriteAttributeString(property.Key, property.Value);
             }

Microsoft.Toolkit.Uwp.Notifications/Toasts/Elements/Element_Toast.cs

@@ -7,7 +7,7 @@
 
 namespace Microsoft.Toolkit.Uwp.Notifications
 {
-    internal sealed class Element_Toast : BaseElement, IElement_ToastActivatable, IHaveAdditionalProperties, IHaveXmlName, IHaveXmlNamedProperties
+    internal sealed class Element_Toast : BaseElement, IElement_ToastActivatable, IHaveXmlAdditionalProperties, IHaveXmlName, IHaveXmlNamedProperties
     {
         internal const ToastScenario DEFAULT_SCENARIO = ToastScenario.Default;
         internal const Element_ToastActivationType DEFAULT_ACTIVATION_TYPE = Element_ToastActivationType.Foreground;

Microsoft.Toolkit.Uwp.Notifications/Toasts/Elements/Element_ToastText.cs

@@ -6,7 +6,7 @@
 
 namespace Microsoft.Toolkit.Uwp.Notifications
 {
-    internal sealed class Element_ToastText : IElement_ToastBindingChild, IHaveXmlName, IHaveXmlNamedProperties
+    internal sealed class Element_ToastText : IElement_ToastBindingChild, IHaveXmlName, IHaveXmlNamedProperties, IHaveXmlText
     {
         internal const ToastTextPlacement DEFAULT_PLACEMENT = ToastTextPlacement.Inline;